Centrifugal casting molds, etc.



Sept V17 l957 y J. JANSEN 2,806,267

CENTRIFUGAL CASTING HOLDS, ETc

vF1106. Feb. 14, 1957- 2 Sheets-Sheet 1 Pfg. f

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CENTRIFUGAL CASTING HOLDS. ETC

Flad Feb. 14. 1957 2 Sheets-Sheet 2 KOI Inventar? Jkavmes Tamek nited States Patent O asoma? cnrirmrucat casrrNo MoLDs, ETC.

Johannes Jansen, Bochum, Germany, assignor to Bochumer Verein Fuer Gusstahlfabrikation Aktiengesellschaft, Bochum, Germany Application February 14, 1957, Serial No. 640,101

12 Claims. (Cl. 22-113.5)

The present invention relates to centrifugal casting molds and processes for making the same.

This application is a continua-tion in part of my copending application Serial No. 314,292, tiled October 11, 1952, and having the title Centrifugal Casting Molds and Processes vfor Making the Same, now abandoned.

in the use of centrifugal casting molds, for making seamless cast iron pipe, for example, it is necessary for the molds to be cooled to permit continuous operation thereof.

This cooling is usually provided in the form of a water,

jacket which is located about the outer surface of the turning mold. When one -considers that the inner surface of such a mold, during use thereof, is placed at a temperature of 1100-1200D C., when molten gray cast iron is placed within the mold, it is apparent that the mold wall is subject t-o tremendous stresses. Because of the cooling of the outer surface -of the mold, the heated inner surface thereof can only expand inwardly toward the axis of the mold and therefore this inner sur-face becomes upset. On the other'hand, the metal of the mold is incapable of cooling quickly enough adjacent its inner surface .to prevent the formation of cracks during the cooling of such a mold, and these cracks general-ly extend in the direction of the length of the mold. Such molds, which may have a wall thickness of 30-40 mm., cannot be 'used many times, and if a crack should unexpectedly occur during use of such a mold, t-he molten metal in the interior of the latter comes in contact with the cooling water andan explosion results.`

One of the objects of the present invention is to overcome all of the above disadvantages by providing a centrifugal casting mold with an inner surface which isV capable of expanding and contracting without causing undue stresses in the mold.

A further object of the present invention is to provide a centrifugal casting mold with an inner mold surface which is capable of expanding and contracting without damaging the mold and which at the same time presents a smooth inner surface to the molten metal being molded.

Another object of the present invention is to provide an inner surface portion of a centrifugal casting mold with a means for guaranteeing that .the inner surface portion will retain its particular form despite expansion and contraction thereof.

An additional object of the present invention is to procide a process for inexpensively, eiciently, and simply manufacturing a centrifugal casting mold capable of accomplishing all of the above objects.

A still further object of the present invention is to provide a centrifugal casting mold which is capable of having only a damaged part thereof easily and quickly repaired or replaced without necessitating vhandling of undamaged parts of the mold. Y

With the above objects in view, the present inventio mainly consists of an elongated, tubular, centrifugal casting mold having an inner surface portion formedtwith a plurality of grooves which are of a lesser-'width at the inner surface of the mold than immediately beneath said inner surface -t-o form at said inner surfacenarrow gaps between their opposite edges, said gaps -being adapted to ICC close due to thermal expansion of the areas between the grooves when the mold is heated during use thereof. These grooves may advantageously be formed on the inner surface of a 'lining which may .take the form of a helically wound metallic band or of a plurality of metallic rings located next to each other.

Also with the above objects in view, the present invention mainly consists of a process for manufacturing a centrifugal casting mold, .this process comprising the steps of forming in the interior surface portion of an elongated tubular mold a plurality of grooves, and app-lying pressure to the interior surface of this mold to narrow lthe grooves at this inner surface so as to produce a plurality of narrow gaps between their opposite edges, said gaps Abeing adapted to close due to thermal expansion of the areas between the grooves when the inner surface is heated by a molten metal placed within the mold. This mold is advantageously formed from an outer casing into which a lining is placed, this lining having the grooves formed on the inner surface thereof before being placed within the casing.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. l is a fragmentary sectional view through an end portion of a centrifuga-l casting mold -constructed in accordance with the present invention;

Fig. 2 is a fragmentary sectional view through a slightly different embodiment of a centrifugal casting mold constructed in accordance with the present invention;

Fig. 3 is a partly sectional, fragmentary view of still another embodiment of a centrifugal mold constructed in accordance with the present invention;

IFig. 4 is a fragmentary view of a part of the mold of Fig. 3 during the manufacture thereof;

Fig. 5 is a fragmentary view of a part of the structure of Fig. 4 taken along the line 5 5 of Fig. 4 in the direction of the arrows;

Fig. 6 is a fragmentary, sectional view of still another embodiment of a mold constructed in accordance with the present invention; and

Fig. 7 is a side view of one of the parts of the mold illustrated in Fig. 6.

Referring now to the drawings, there is shown in Fig. l a par-t of a mold having grooves 9 and 10 formed on the inner surface thereof. These grooves 9 and 10 intersect each other at angles of about to 100J and are distributed over the inner surface of the mold. The grooves 9 and 10 are of a special construction in that they are narrower at the inner mold surface than immediately -beneath this surface and thus form at the inner mold surface very narrow gaps between their opposite edges, said gaps 'being adapted to close due to thermal expansion of the areas between the grooves when the inner mold surface is heated during use of the mold. The narrower width of the grooves 9 and 10 at the inner surface of the mold may 'be produced by applying a pressure to the inner mold surface, preferably by cold working the latter so as to strengthen the material of the mold at this inner mol-d surface. This pressure may be produced by applying a roller or the like with a sufficient force against the inner mold surface or by pressing suitable dies or polishing instruments against the latter.

In order to make up for the loss of heat conductivity caused .by the removal of material in cutting the grooves, and in order to ll the grooves Iso as to prevent the casting material from penetrating in its liquid state into the essary, for instance if there is` a difference between the outer diameter of the coil and the inner diameter of the outer tubular member. After this, the coil is pushed into the tubular member and is attached to opposite ends of the mold by suitable means like screws, rivets, or even by welding, whereafter the mandrel can be forced out. Now, the lined mold is ready for machining the inner surface. The inner diameter may be increased by turning or grinding so as to increase the rough inner diameter by .039 to the desired nal inner diameter. In this manner, after turning or grinding the inner surf-ace, the depth of the individual grooves is approximately .315". Consequently, the finished mold has an inner diameter of 13.639" and an outer diameter of 18".

During the coiling operation, the shape of the originally straight grooves is changed because the edges of the grooves are forced towards each other, yand at the same time the insert of metal powder is substantially compressed. It is to be noted that the reduction of the gap between opposite edges of a particular groove is not prevented by the presence of the metal powder. After machining the inside of the lining to finished dimensions, the inner surface appears as being entirely closed and free of gaps.

When the mold is first put to use, its inner zone expands considerably and causes compression of all the mold material exposed to the higher temperatures. Under these conditions, the opposing edges of the grooves are subjected to very high stresses due to the compression caused by thermal expansion. This condition exists as long as the inner surface of the mold is exposed to the prevailing temperatures. Under the influence of these pressure stresses the material has a tendency to creep which is due to the fact that the mold is continually exposed to certain changes in temperature. When the molten iron contacts the inner surface of the mold, it heats it up to high temperatures which, however, drop again rapidly soon thereafter. It is true that the temperature of the mold surface does not drop below a certain average temperature during continuous use of the mold, however conditions change entirely when the mold is taken out of service and cooled to room temperature. Under this condition the grooves do not remain tightly closed any more but -open up depending upon the conn traction of the surface area located between two consecutive grooves. It is within the scope of this invention to make these surface areas large enough in order to provide for ample breathing of the surface without risking too great an opening of the grooves when the mold finally cools down.

Whenever, at any times, the mold is put to use again, a rapid closing of the grooves before casting can be obtained by preheating the mold, for instance, with the aid of a gas or oil burner. However, this is not necessary if the inner surface is powdered with a silicon powder.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of centrifugal casting molds and processes for making the same differing from the types described above.

While the invention has been illustrated and described as embodied in centrifugal casting molds having removable liners and processes for making the same, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended equivalence of the following claims.

What is claimed as new and desired to be secured by- Letters Patent is:

l. An elongated, tubular centrifugal casting mold hav-l ing an inner surface portion formed with a plurality ofk grooves which are of a lesser `width at the inner surface of the mold than immediately beneath said inner surface to form at said inner surface narrow gaps between their opposite edges, said gaps -being adapted to close when the mold is heated during use thereof; and heat-conductive means located in said grooves for keeping the edges of the latter, at the inner surface of the mold, apart from each other.

2. An elongated, tubular centrifugal casting mold having an inner surface portion formed with a plurality of grooves which are of a lesser width at the inner surface of the mold than immediately beneath said inner surface to form at said inner surface narrow gaps between their opposite edges, said gaps being adapted to close when the mold is heated during use thereof; and heat-conductive means located in said grooves for keeping the edges of the latter, at the inner surface of the mold, apart from each other, said means being in the form of a metal different from the material of the mold and located within said grooves.

3. A process for manufacturing a centrifugal casting mold 'comprising the steps of forming in the inner surface portion of an elongated tubular mold a plurality of grooves; placing a pressure-resistant heat-conductive means within said grooves; and applying pressure to said inner surface to narrow said grooves about said pressureresistant heat-conductive means so as to produce at said inner surface a plurality of narrow gaps between their opposite edges, said gaps being adapted to close when said inner surface is heated by a molten metal placed within the mold.

4. A centrifugal casting mold comprising, in combination, an elongated, rigid, tubular member; a lining located within said tubular member and against the same, said lining having its inner surface portion formed with a plurality of grooves which are of a lesser width at said inner surface of said lining than immediately beneath said inner surface of said lining so as to form at said inner surface of said lining a plurality of narrow gaps between their opposite edges, said gaps being adapted to close when the mold is heated during use thereof; and a heatconductive metallic material located in said grooves.

5. A process for manufacturing a centrifugal casting mold, comprising the steps of forming a plurality of grooves on one side of an elongated band of metal; curving said band along a helix with the convolutions of the band located against each other, to form a tube from said band, and with said one side of said band forming the inner surface of said tube, so as to thereby cold work said inner surface to narrow said grooves at said inner surface; and placing Said thus formed tube in the interior of a second tube and against the inner surface of the latter.

6. A process for manufacturing a centrifugal casting mold, comprising the steps of forming on the inner surface of each of a plurality of identical rings a plurality of grooves; cold working the inner surface of each ring to narrow the grooves therein at the inner surface of each ring; and placing said rings next to each other within a rigid tubular member having an inner diameter substantially equal to the outer diameter of said rings, so that the latter form a lining on the interior of said tubular member.

7. A centrifugal casting mold comprising, in combination, an elongated, rigid, tubular member; and a lining located within said tubular member and against the same, said lining having its inner surface portion formed with a plurality of grooves and said lining being in the form of an elongated metallic band which is helically wound so as to form a cylinder.

8. A centrifugal casting mold comprising, in combinadan, an elongated, rind,tdbd1nf miaeag- @ddl d1 lining-'l located within said tubfiil'a' memberaridiagainstlthime;

located'Within'v saidtubulai" member and.I against tile/saine;v

saidllining having its inner siirfa'cporti'on forrii'e'dwith" a plurality of grooves and sidliniri'gbingfin the forrnof an elongated metallic bandwhicliishelieally Wound s`oasv to forni a` cylinder, said grooves li'aviriga lsser Width aty the inner surface of said lining than immediately beneath said" inner surface.

l;y A centrifugal' casting-'mold comprising, in combina'- tion; an elongated,'frig`id, tubular member; a'nd'af lining located Within said tubular member ai'ldagairistthe same, saidlining havingitsinner surfaee'prtion formedvvith a plurality of grooves andsaid'linirigbeiiigf inthe form of apluralityl ofv identicalmetallic Iings'locatednext to each other within said'tubular member' so as'toifbr'm a'cylinder, saidgrooves havingalesser Width a't the inner' surface'of said lining than immediately beneath said; inner surface.

11'. A' centrifugal casting mo'ld comprising; in'combina'l tion, an elongated, rigid, tubular member; a liriiriglocated within said tubular member and againstthe same, said lining having its innerv surface portion formed with a p'lurality of grooves and said liningbeing inthe form of aji eldgjted dietu'ief band waren is helicuy wound so' to1 formacylinder, grov'es having a-lelsse'r Width at; the inner surface of said lining than immediately beneath said inner surfa'cejand ariinzs'ert'loeated Within-said grooves andzbein'g'made of a' material' different fromthev rriat'erialof said lining; l

12`. AL centrifugal'castingmold comprising-in combination, an elongated, rigid,ltublar member-a lining located n Within *saidV tubular m'eriibe'r and against the same, said References Cited: in the tile' of this patent UNITED sTATEs PATENTS `609,460 Pipje'rs' Aug. 23', 184s 1,485,859' Ladd Map. 4, 1924 1,523,021 Ladd T Jan. 13, 1925v 2,577,423 Ludwig' Dee. 4, 1951 FOREIGN PATENTS 

